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Preweaning mortalities represent a significant economic loss to the U.S. swine sector. PigChamp preweaning mortality records show U.S. sow herds averaged 12.2% in the first quarter of 2009.

It is widely accepted that the injury and crushing incidents causing these piglet deaths occur when the sow attempts to lie down within the confines of the farrowing crate. Researchers at the University of Minnesota wondered what role claw (foot) lesions played in these losses.

“Claw lesions are generally believed to be painful,” explains research team member Leena Anil. Logically, painful foot lesions could restrict the sows’ agility and lead to more crushed and injured piglets.

“The front legs are nearer the center of gravity,” she adds, noting that as a sow attempts to lie down, more movements are associated with their front legs than their back legs.

To learn more, Anil and her colleagues, Sam Baidoo, John Deen and S.S.Anil, developed a study to analyze the association of preweaning piglet deaths due to crushing with factors such as claw lesions, sow parity and the effects of housing during gestation. Their study included 611 parity records of sows housed in group pens with electronic sow feeders (ESF) and 399 parity records of sows housed in conventional gestation stalls.

The study was conducted at the University of Minnesota Southern Research and Outreach Center at Waseca, MN, where foot lesions were examined at mid-gestation using a mechanical restraint designed for that purpose. Total claw lesion scores for front and hind limbs were obtained by adding the lesions scores in different claw areas — side wall, heel, sole, heel-sole junction and white line — of the lateral and medial claws (see diagrams, pages 20-21).

Barn staff recorded the reasons for preweaning mortalities, sow parity and gestation housing in the PigChamp database. This information was used to associate piglet mortalities due to crushing with claw lesion scores (front and hind feet), sow parity and gestation housing. Sow records were grouped as Parity 1-2, Parity 3-5, and Parity 6 and higher.

In the study, 24% of preweaning mortalities were reportedly due to crushing. “For every unit increase in claw lesions in front limbs, the number of preweaning piglet death due to crushing increased by 8%,” Anil reports. “A higher hind limb claw lesion score was also associated with the higher number of piglet deaths due to crushing, though this association was not significant.”

Parity 1-2 sows had 61% lower death loss due to crushing than Parity 6 and higher sows, while Parity 3-5 sows had a 36% lower crushing rate than the older-parity sows.

“Sows housed in group pens had 39% fewer piglet deaths due to crushing compared to sows housed in stalls during gestation,” she adds.

Fewer piglet deaths in lower-parity sows could be related to the smaller litter size during these early parities; however, the positive association between front limb lesions and higher death rates caused by crushing is interesting, Anil notes. “This may be suggestive of restriction due to pain in making the necessary postural movements to avoid uncontrolled falling within the farrowing crate, thus leading to a higher number of pigs being crushed,” she notes.